cave
/keɪv; kev/ n
hollow place in the side of a cliff or hill, or underground 洞穴. cave, v
1 [I] (usu 通常作 go caving) explore caves as a sport 洞穴探险运动
He likes caving. 他喜欢洞穴探险运动.
2 (phr v) cave in fall inwards; collapse 塌陷; 坍方; 坍塌
The roof of the tunnel caved in (on the workmen). 隧道顶坍塌（压住工人）.
(fig 比喻) All opposition to the scheme has caved in. 所有反对这一计划的意见都否定了.